Multidirectional acoustic wave transmission via artificial periodic structures

This paper presents a unified artificial periodic structure for multidirectional acoustic wave transmission along complex pathways. The structure employs a two-dimensional, three-component unit cell—consisting of a lead core, rubber cladding, and epoxy matrix—whose resonant dynamics are captured by a double-spring model extended with nonlocal inter-cell coupling corrections. Remarkably, a single lattice configuration, through modest tuning of lattice dimensions, array arrangement, and operating frequency, supports three distinct acoustic functions: negative-refraction-based multidirectional focusing via triangular and polygonal arrays, bandgap-confined directional transmission along straight and curved defect waveguides with switchable beam-splitting behavior, and topologically protected transport exploiting valley edge states. A theoretical framework based on effective-medium parameters and topological band theory (Berry phase and Chern number) is established to elucidate the underlying mechanisms. The predicted transmission characteristics are validated by 500 kHz underwater acoustic experiments on a three-dimensionally printed Z-shaped topological waveguide. The proposed approach is distinguished by its design economy, adaptability, and broad applicability, offering a promising strategy for advanced acoustic wave control with implications for acoustic communication, non-destructive evaluation, and signal detection.